The present invention is dedicated to Georgio Aulisio. He boarded ship from his native Italy and arrived at Ellis Island in the Harbor of New York City in the late 19th century at the age of sixteen. He had six dollars in his pocket. During his lifetime, he was employed in the anthracite coal mines of eastern Pennsylvania.
Prior art methods of mining coal include surface mining and underground mining. In surface mining, a seam of coal located close to the surface of the earth is first exposed by mechanical removal of the earth above the coal seam. A mountaintop, for example, can be removed by employing bulldozers and earthmoving equipment to expose an underground seam of coal. The exposed seam of coal is mined by employing machinery known to one of ordinary skill in the art.
Underground mining includes sinking a shaft into the earth near (or into) a seam of coal. A ventilated area is then constructed within the seam of coal. Ventilation of the underground area allows coal miners to operate mechanical equipment at the face of a coal seam. The coal is then brought to the surface. A preferred method of removing coal from the coal face is the long-wall method of mining. Regardless of the method employed in underground mining, conditions for the miners are very dangerous. Although various safety precautions are taken with regard to the underground mining of coal, accidents occur on a regular basis.
One problem in underground mining of coal is the presence of methane gas in the coal seam. A coal seam is naturally infused with substantial amounts of methane. Methane is the most highly reduced form of carbon, which means that it readily undergoes rapid oxidation. It forms an explosive mixture with oxygen (air). Methane has an upper explosive limit and a lower explosive limit. The upper explosive limit (UEL) for methane is about 15% by volume. The lower explosive limit (LEL) for methane is about 5% by volume. Traditional underground mining operates in a region below the lower explosive limit of methane. Conditions in an underground mine can be monitored by employing a “bug lamp”. The “bug lamp” burns with a bright yellow flame when the composition of the atmosphere at the face of a coal seam is such that it is below the LEL of methane. When the “bug lamp” burns with a blue cap above the yellow flame, the underground atmosphere is above the LEL of methane. This signifies extremely dangerous conditions. Ventilation with above-ground air is immediately increased to remove the dangerous conditions. Mining operations cease when the atmospheric condition in the underground mine is above the LEL of methane.